You must be logged in to access this feature.

Your next patient, set to undergo a femoral bypass, has a history of myocardial infarction. You are planning to incorporate nitrous oxide into the anesthetic. The Evaluation of Nitrous Oxide in the Gas Mixture for Anaesthesia (ENIGMA)-II trial evaluated risks associated with the use of nitrous oxide in patients with cardiac risk factors undergoing noncardiac surgery. Which of the following best describes the findings of the ENIGMA-II trial regarding the use of nitrous oxide?

The initial ENIGMA trial suggested that patients who were exposed to nitrous oxide had higher cardiovascular morbidity one year later. In that study, a total of 2,050 unselected, low-cardiac-risk patients were randomized to 80 percent oxygen/20 percent nitrogen or 70 percent nitrous oxide/30 percent oxygen. The primary outcome was duration of hospital stay, and secondary outcomes were duration of intensive care unit stay and postoperative complications such as pneumonia, pneumothorax, pulmonary embolism, wound infection, myocardial infarction, venous thromboembolism, stroke, awareness, and death. Those in the nitrous oxide–free group had a lower risk of major complications and postoperative nausea and vomiting. Median length of hospital stay was not different between the groups. The number of confirmed myocardial infarctions was greater in the nitrous oxide group compared to the control group.